Src homology 2 (SH2) domain; In general, SH2 domains are involved in signal transduction; they bind pTyr-containing polypeptide ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites. They are present in a wide array of proteins including: adaptor proteins (Nck1, Crk, Grb2), scaffolds (Slp76, Shc, Dapp1), kinases (Src, Syk, Fps, Tec), phosphatases (Shp-1, Shp-2), transcription factors (STAT1), Ras signaling molecules (Ras-Gap), ubiquitination factors (c-Cbl), cytoskeleton regulators (Tensin), signal regulators (SAP), and phospholipid second messengers (PLCgamma), amongst others.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 7295405  248 PWYQPRITAKAALEHLQQATPGSFLLRRSTPRHFELVLRL-ERNNKVKTYPVQSTRNQMYRLKGAKKQFTSLKALITHH 325
Cdd:cd00173   1 PWFHGSISREEAERLLRGKPDGTFLVRESSSEPGDYVLSVrSGDGKVKHYLIERNEGGYYLLGGSGRTFPSLPELVEHY 79

Src homology 2 (SH2) domain; In general, SH2 domains are involved in signal transduction; they bind pTyr-containing polypeptide ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites. They are present in a wide array of proteins including: adaptor proteins (Nck1, Crk, Grb2), scaffolds (Slp76, Shc, Dapp1), kinases (Src, Syk, Fps, Tec), phosphatases (Shp-1, Shp-2), transcription factors (STAT1), Ras signaling molecules (Ras-Gap), ubiquitination factors (c-Cbl), cytoskeleton regulators (Tensin), signal regulators (SAP), and phospholipid second messengers (PLCgamma), amongst others.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 7295405  248 PWYQPRITAKAALEHLQQATPGSFLLRRSTPRHFELVLRL-ERNNKVKTYPVQSTRNQMYRLKGAKKQFTSLKALITHH 325
Cdd:cd00173   1 PWFHGSISREEAERLLRGKPDGTFLVRESSSEPGDYVLSVrSGDGKVKHYLIERNEGGYYLLGGSGRTFPSLPELVEHY 79

SH2 domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405    249 WYQPRITAKAALEHLQQA-TPGSFLLR--RSTPRHFELVLRleRNNKVKTYPVQSTRNQMYRLKGAKKqFTSLKALITHH 325
Cdd:pfam00017   1 WYHGKISRQEAERLLLNGkPDGTFLVResESTPGGYTLSVR--DDGKVKHYKIQSTDNGGYYISGGVK-FSSLAELVEHY 77

Src homology 2 (SH2) domain; In general, SH2 domains are involved in signal transduction; they bind pTyr-containing polypeptide ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites. They are present in a wide array of proteins including: adaptor proteins (Nck1, Crk, Grb2), scaffolds (Slp76, Shc, Dapp1), kinases (Src, Syk, Fps, Tec), phosphatases (Shp-1, Shp-2), transcription factors (STAT1), Ras signaling molecules (Ras-Gap), ubiquitination factors (c-Cbl), cytoskeleton regulators (Tensin), signal regulators (SAP), and phospholipid second messengers (PLCgamma), amongst others.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 7295405  248 PWYQPRITAKAALEHLQQATPGSFLLRRSTPRHFELVLRL-ERNNKVKTYPVQSTRNQMYRLKGAKKQFTSLKALITHH 325
Cdd:cd00173   1 PWFHGSISREEAERLLRGKPDGTFLVRESSSEPGDYVLSVrSGDGKVKHYLIERNEGGYYLLGGSGRTFPSLPELVEHY 79

Src homology 2 domain found in Tensin-like proteins; SH2 domain found in Tensin-like proteins. The Tensins are a family of intracellular proteins that interact with receptor tyrosine kinases (RTKs), integrins, and actin. They are thought act as signaling bridges between the extracellular space and the cytoskeleton. There are four homologues: Tensin1, Tensin2 (TENC1, C1-TEN), Tensin3 and Tensin4 (cten), all of which contain a C-terminal tandem SH2-PTB domain pairing, as well as actin-binding regions that may localize them to focal adhesions. The isoforms of Tensin2 and Tensin3 contain N-terminal C1 domains, which are atypical and not expected to bind to phorbol esters. Tensins 1-3 contain a phosphatase (PTPase) and C2 domain pairing which resembles PTEN (phosphatase and tensin homologue deleted on chromosome 10) protein. PTEN is a lipid phosphatase that dephosphorylates phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) to yield phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). As PtdIns(3,4,5)P3 is the product of phosphatidylinositol 3-kinase (PI3K) activity, PTEN is therefore a key negative regulator of the PI3K pathway. Because of their PTEN-like domains, the Tensins may also possess phosphoinositide-binding or phosphatase capabilities. However, only Tensin2 and Tensin3 have the potential to be phosphatases since only their PTPase domains contain a cysteine residue that is essential for catalytic activity. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405  249 WYQPRITAKAALEHLQQATPGSFLLRRST--PRHFELVLRLERN--NKVKTYPVQSTRNQMYR------------LKGAK 312
Cdd:cd09927   5 WYKPNISRDQAIALLKDKPPGTFLVRDSTtyKGAYGLAVKVATPppGVNPFEAKGDPESELVRhfliepspkgvkLKGCP 84

                        90       100
                ....*....|....*....|....*....
gi 7295405  313 KQ--FTSLKALITHHSVMAEQLPLVLDMP 339
Cdd:cd09927  85 NEpvFGSLSALVYQHSITPLALPCKLRIP 113

SH2 domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405    249 WYQPRITAKAALEHLQQA-TPGSFLLR--RSTPRHFELVLRleRNNKVKTYPVQSTRNQMYRLKGAKKqFTSLKALITHH 325
Cdd:pfam00017   1 WYHGKISRQEAERLLLNGkPDGTFLVResESTPGGYTLSVR--DDGKVKHYKIQSTDNGGYYISGGVK-FSSLAELVEHY 77

C-terminal Src homology 2 (SH2) domain found in SH2 domains, ANK, and kinase domain (shark) proteins; These non-receptor protein-tyrosine kinases contain two SH2 domains, five ankyrin (ANK)-like repeats, and a potential tyrosine phosphorylation site in its carboxyl-terminal tail which resembles the phosphorylation site in members of the src family. Like, mammalian non-receptor protein-tyrosine kinases, ZAP-70 and syk proteins, they do not have SH3 domains. However, the presence of ANK makes these unique among protein-tyrosine kinases. Both tyrosine kinases and ANK repeats have been shown to transduce developmental signals, and SH2 domains are known to participate intimately in tyrosine kinase signaling. These tyrosine kinases are believed to be involved in epithelial cell polarity. The members of this family include the shark (SH2 domains, ANK, and kinase domain) gene in Drosophila and yellow fever mosquitos, as well as the hydra protein HTK16. Drosophila Shark is proposed to transduce intracellularly the Crumbs, a protein necessary for proper organization of ectodermal epithelia, intercellular signal. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405  249 WYQPRITAKAALEHLQQA--TPGSFLLRRSTPRHFELVLRLERNNKVKTYPVQSTRNQMYRLKGAkKQFTSLKALITHHS 326
Cdd:cd10348   2 WLHGALDRNEAVEILKQKadADGSFLVRYSRRRPGGYVLTLVYENHVYHFEIQNRDDKWFYIDDG-PYFESLEHLIEHYT 80

                ....*.
gi 7295405  327 VMAEQL 332
Cdd:cd10348  81 QFADGL 86

Src homology 2 (SH2) domain found in Ras and Rab interactor (RIN)-family; The RIN (AKA Ras interaction/interference) family is composed of RIN1, RIN2 and RIN3. These proteins have multifunctional domains including SH2 and proline-rich (PR) domains in the N-terminal region, and RIN-family homology (RH), VPS9 and Ras-association (RA) domains in the C-terminal region. RIN proteins function as Rab5-GEFs, and RIN3 specifically functions as a Rab31-GEF. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405  244 LLACP-WYQPRITAKAALEHLQQATPGSFLLRRSTPRHFE-LVLRL---ERNNKVKTYPVQSTRNQMYrLKGAKKQFTSL 318
Cdd:cd10339   6 LLTRPvWLQLQLNAAEAAHMLQTEPPGTFLVRKSNTRQCQvLCMRLpeaSGPAFVSEHYIKESPGGVS-LEGSELMFPDL 84

                        90
                ....*....|....*.
gi 7295405  319 KALITHHSVMAEQLPL 334
Cdd:cd10339  85 FRLIAFYCHSRDILPF 100

Src homology 2 (SH2) domain found in Ras and Rab interactor 1 (RIN1)-like proteins; RIN1, a member of the RIN (AKA Ras interaction/interference) family, have multifunctional domains including SH2 and proline-rich (PR) domains in the N-terminal region, and RIN-family homology (RH), VPS9 and Ras-association (RA) domains in the C-terminal region. RIN proteins function as Rab5-GEFs. Previous studies showed that RIN1 interacts with EGF receptors via its SH2 domain and regulates trafficking and degradation of EGF receptors via its interaction with STAM, indicating a vital role for RIN1 in regulating endosomal trafficking of receptor tyrosine kinases (RTKs). RIN1 was first identified as a Ras-binding protein that suppresses the activated RAS2 allele in S. cerevisiae. RIN1 binds to the activated Ras through its carboxyl-terminal domain and this Ras-binding domain also binds to 14-3-3 proteins as Raf-1 does. The SH2 domain of RIN1 are thought to interact with the phosphotyrosine-containing proteins, but the physiological partners for this domain are unknown. The proline-rich domain in RIN1 is similar to the consensus SH3 binding regions. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405  249 WYQPRITAKAALEHLQQATPGSFLLRRSTPRHFE-LVLRLERNNK---VKTYPVQSTRNQMYrLKGAKKQFTSLKALITH 324
Cdd:cd10393  12 WLQLRANAAAALHVLRTEPPGTFLVRKSNTRQCQaLCVRLPEASGpsfVSSHYIQESPGGVS-LEGSELTFPDLVQLICA 90

                        90
                ....*....|
gi 7295405  325 HSVMAEQLPL 334
Cdd:cd10393  91 YCHTRDILLL 100

N-terminal Src homology 2 (N-SH2) domain found in SH2 domain Phosphatases (SHP) proteins; The SH2 domain phosphatases (SHP-1, SHP-2/Syp, Drosophila corkscrew (csw), and Caenorhabditis elegans Protein Tyrosine Phosphatase (Ptp-2)) are cytoplasmic signaling enzymes. They are both targeted and regulated by interactions of their SH2 domains with phosphotyrosine docking sites. These proteins contain two SH2 domains (N-SH2, C-SH2) followed by a tyrosine phosphatase (PTP) domain, and a C-terminal extension. Shp1 and Shp2 have two tyrosyl phosphorylation sites in their C-tails, which are phosphorylated differentially by receptor and nonreceptor PTKs. Csw retains the proximal tyrosine and Ptp-2 lacks both sites. Shp-binding proteins include receptors, scaffolding adapters, and inhibitory receptors. Some of these bind both Shp1 and Shp2 while others bind only one. Most proteins that bind a Shp SH2 domain contain one or more immuno-receptor tyrosine-based inhibitory motifs (ITIMs): [IVL]xpYxx[IVL]. Shp1 N-SH2 domain blocks the catalytic domain and keeps the enzyme in the inactive conformation, and is thus believed to regulate the phosphatase activity of SHP-1. Its C-SH2 domain is thought to be involved in searching for phosphotyrosine activators. The SHP2 N-SH2 domain is a conformational switch; it either binds and inhibits the phosphatase, or it binds phosphoproteins and activates the enzyme. The C-SH2 domain contributes binding energy and specificity, but it does not have a direct role in activation. Csw SH2 domain function is essential, but either SH2 domain can fulfill this requirement. The role of the csw SH2 domains during Sevenless receptor tyrosine kinase (SEV) signaling is to bind Daughter of Sevenless rather than activated SEV. Ptp-2 acts in oocytes downstream of sheath/oocyte gap junctions to promote major sperm protein (MSP)-induced MAP Kinase (MPK-1) phosphorylation. Ptp-2 functions in the oocyte cytoplasm, not at the cell surface to inhibit multiple RasGAPs, resulting in sustained Ras activation. It is thought that MSP triggers PTP-2/Ras activation and ROS production to stimulate MPK-1 activity essential for oocyte maturation and that secreted MSP domains and Cu/Zn superoxide dismutases function antagonistically to control ROS and MAPK signaling. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405  249 WYQPRITAKAALEHLQQ-ATPGSFLLR--RSTPRHFELVLRleRNNKVKTYPVQSTrNQMYRLKGAKKqFTSLKALITHH 325
Cdd:cd10340   2 WFHPVISGIEAENLLKTrGVDGSFLARpsKSNPGDFTLSVR--RGDEVTHIKIQNT-GDYYDLYGGEK-FATLSELVQYY 77

                ....*..
gi 7295405  326 SVMAEQL 332
Cdd:cd10340  78 MEQHGQL 84

C-terminal Src homology 2 (C-SH2) domain found in SH2 domain Phosphatases (SHP) proteins; The SH2 domain phosphatases (SHP-1, SHP-2/Syp, Drosophila corkscrew (csw), and Caenorhabditis elegans Protein Tyrosine Phosphatase (Ptp-2)) are cytoplasmic signaling enzymes. They are both targeted and regulated by interactions of their SH2 domains with phosphotyrosine docking sites. These proteins contain two SH2 domains (N-SH2, C-SH2) followed by a tyrosine phosphatase (PTP) domain, and a C-terminal extension. Shp1 and Shp2 have two tyrosyl phosphorylation sites in their C-tails, which are phosphorylated differentially by receptor and nonreceptor PTKs. Csw retains the proximal tyrosine and Ptp-2 lacks both sites. Shp-binding proteins include receptors, scaffolding adapters, and inhibitory receptors. Some of these bind both Shp1 and Shp2 while others bind only one. Most proteins that bind a Shp SH2 domain contain one or more immuno-receptor tyrosine-based inhibitory motifs (ITIMs): [SIVL]xpYxx[IVL]. Shp1 N-SH2 domain blocks the catalytic domain and keeps the enzyme in the inactive conformation, and is thus believed to regulate the phosphatase activity of SHP-1. Its C-SH2 domain is thought to be involved in searching for phosphotyrosine activators. The SHP2 N-SH2 domain is a conformational switch; it either binds and inhibits the phosphatase, or it binds phosphoproteins and activates the enzyme. The C-SH2 domain contributes binding energy and specificity, but it does not have a direct role in activation. Csw SH2 domain function is essential, but either SH2 domain can fulfill this requirement. The role of the csw SH2 domains during Sevenless receptor tyrosine kinase (SEV) signaling is to bind Daughter of Sevenless rather than activated SEV. Ptp-2 acts in oocytes downstream of sheath/oocyte gap junctions to promote major sperm protein (MSP)-induced MAP Kinase (MPK-1) phosphorylation. Ptp-2 functions in the oocyte cytoplasm, not at the cell surface to inhibit multiple RasGAPs, resulting in sustained Ras activation. It is thought that MSP triggers PTP-2/Ras activation and ROS production to stimulate MPK-1 activity essential for oocyte maturation and that secreted MSP domains and Cu/Zn superoxide dismutases function antagonistically to control ROS and MAPK signaling. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405  249 WYQPRITAKAALEHLQ-QATPGSFLLR--RSTPRHFELVLRLErNNKVKTYPVqstRNQMYRLK-GAKKQFTSLKALITH 324
Cdd:cd09931   2 WFHGHLSGKEAEKLLLeKGKPGSFLVResQSKPGDFVLSVRTD-DDKVTHIMI---RCQGGKYDvGGGEEFDSLTDLVEH 77

                ..
gi 7295405  325 HS 326
Cdd:cd09931  78 YK 79

Src homology 2 (SH2) domain found in Ras and Rab interactor 3 (RIN3)-like proteins; RIN3, a member of the RIN (AKA Ras interaction/interference) family, have multifunctional domains including SH2 and proline-rich (PR) domains in the N-terminal region, and RIN-family homology (RH), VPS9 and Ras-association (RA) domains in the C-terminal region. RIN proteins function as Rab5-GEFs. RIN3 stimulated the formation of GTP-bound Rab31, a Rab5-subfamily GTPase, and formed enlarged vesicles and tubular structures, where it colocalized with Rab31. Transferrin appeared to be transported partly through the RIN3-positive vesicles to early endosomes. RIN3 interacts via its Pro-rich domain with amphiphysin II, which contains SH3 domain and participates in receptor-mediated endocytosis. RIN3, a Rab5 and Rab31 GEF, plays an important role in the transport pathway from plasma membrane to early endosomes. Mutations in the region between the SH2 and RH domain of RIN3 specifically abolished its GEF action on Rab31, but not Rab5. RIN3 was also found to partially translocate the cation-dependent mannose 6-phosphate receptor from the trans-Golgi network to peripheral vesicles and that this is dependent on its Rab31-GEF activity. These data indicate that RIN3 specifically acts as a GEF for Rab31. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405  247 CP-WYQPRITAKAALEHLQQATPGSFLLRR-STPRHFELVLRLERNN---KVKTYPVQSTRNQMYrLKGAKKQFTSLKAL 321
Cdd:cd10395   9 CPvWLQLGMNQAEAARILHKEVAGMFLVRRdSNSKQMVLCVHFPSNEssaEVLEYPIKEEKSILY-LEGSVLVFEDIFKL 87

                        90
                ....*....|..
gi 7295405  322 ITHHSVMAEQLP 333
Cdd:cd10395  88 IAFYCVSRDLLP 99

Src homology 2 (SH2) domain in lymphocyte cell kinase (Lck); Lck is a member of the Src non-receptor type tyrosine kinase family of proteins. It is expressed in the brain, T-cells, and NK cells. The unique domain of Lck mediates its interaction with two T-cell surface molecules, CD4 and CD8. It associates with their cytoplasmic tails on CD4 T helper cells and CD8 cytotoxic T cells to assist signaling from the T cell receptor (TCR) complex. When the T cell receptor is engaged by the specific antigen presented by MHC, Lck phosphorylase the intracellular chains of the CD3 and zeta-chains of the TCR complex, allowing ZAP-70 to bind them. Lck then phosphorylates and activates ZAP-70, which in turn phosphorylates Linker of Activated T cells (LAT), a transmembrane protein that serves as a docking site for proteins including: Shc-Grb2-SOS, PI3K, and phospholipase C (PLC). The tyrosine phosphorylation cascade culminates in the intracellular mobilization of a calcium ions and activation of important signaling cascades within the lymphocyte, including the Ras-MEK-ERK pathway, which goes on to activate certain transcription factors such as NFAT, NF-kappaB, and AP-1. These transcription factors regulate the production cytokines such as Interleukin-2 that promote long-term proliferation and differentiation of the activated lymphocytes. The N-terminal tail of Lck is myristoylated and palmitoylated and it tethers the protein to the plasma membrane of the cell. Lck also contains a SH3 domain, a SH2 domain, and a C-terminal tyrosine kinase domain. Lck has 2 phosphorylation sites, the first an autophosphorylation site that is linked to activation of the protein and the second which is phosphorylated by Csk, which inhibits it. Lck is also inhibited by SHP-1 dephosphorylation and by Cbl ubiquitin ligase, which is part of the ubiquitin-mediated pathway. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 7295405  248 PWYQPRITAKAALEHL--QQATPGSFLLRRS--TPRHFELVLR-LERN--NKVKTYPVQSTRNQMYRLKgAKKQFTSLKA 320
Cdd:cd10362   4 PWFFKNLSRNDAERQLlaPGNTHGSFLIRESetTAGSFSLSVRdFDQNqgEVVKHYKIRNLDNGGFYIS-PRITFPGLHE 82

                        90
                ....*....|....*....
gi 7295405  321 LITHHSVMAEQLPLVLDMP 339
Cdd:cd10362  83 LVRHYTNASDGLCTRLSRP 101

Src homology 2 (SH2) domain in the Janus kinase (Jak) family; The Janus kinases (Jak) are a family of 4 non-receptor tyrosine kinases (Jak1, Jak2, Jak3, Tyk2) which respond to cytokine or growth factor receptor activation. To transduce cytokine signaling, a series of conformational changes occur in the receptor-Jak complex upon extracellular ligand binding. This results in trans-activation of the receptor-associated Jaks followed by phosphorylation of receptor tail tyrosine sites. The Signal Transducers and Activators of Transcription (STAT) are then recruited to the receptor tail, become phosphorylated and translocate to the nucleus to regulate transcription. Jaks have four domains: the pseudokinase domain, the catalytic tyrosine kinase domain, the FERM (band four-point-one, ezrin, radixin, and moesin) domain, and the SH2 (Src Homology-2) domain. The Jak kinases are regulated by several enzymatic and non-enzymatic mechanisms. First, the Jak kinase domain is regulated by phosphorylation of the activation loop which is associated with the catalytically competent kinase conformation and is distinct from the inactive kinase conformation. Second, the pseudokinase domain directly modulates Jak catalytic activity with the FERM domain maintaining an active state. Third, the suppressor of cytokine signaling (SOCS) family and tyrosine phosphatases directly regulate Jak activity. Dysregulation of Jak activity can manifest as either a reduction or an increase in kinase activity resulting in immunodeficiency, inflammatory diseases, hematological defects, autoimmune and myeloproliferative disorders, and susceptibility to infection. Altered Jak regulation occurs by many mechanisms, including: gene translocations, somatic or inherited point mutations, receptor mutations, and alterations in the activity of Jak regulators such as SOCS or phosphatases. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 7295405  268 PGSFLLRRStPRHF-----ELVLRLERNNKVKTYPVQSTRNQMYRLKGAKKQFTSLKALITH 324
Cdd:cd09921  35 PGSYILRES-ETEYdtyyiDVCVKDGSRFQTKTFKIEKKEGGVFFLDGDSREYPSLRDLLNS 95